1. Field of the Invention
The invention relates to a sensor system as claimed in claim 1 for a magnetic bearing, to a regulation device as claimed in claim 10 for a magnetic bearing, a magnetic bearing as claimed in claim 14, and a method as claimed in claim 15.
2. Description of Related Art
Magnetic bearings are used for contactless guidance and mounting of moving parts such as rotors of motors or impellers of pumps. The lack of touching mechanical contact makes it possible, inter alia, to optimize friction losses, to reduce wear and to avoid the generation of particles. Major components of a magnetic bearing are:                1. An actuator system which comprises one or more electromagnets,        2. A sensor system, which detects the instantaneous position of the object to be mounted and allows regulation at a nominal position, and        3. Electrical components for signal detection, regulation and for control of power flows.        
In general, the sensor system is an assembly which is rigidly coupled to and additionally fitted to the actuator system. In order to optimize the physical size of the magnetic bearing, it is desirable for the sensor system to occupy only a small amount of space, or even to allow this to be dispensed with completely. The use of the effect that the impedance of the actuator coils of the actuator system changes as a function of the position allows the actuator system, which is required in any case, with the actuator coils also to carry out the function of the position sensor. Corresponding technical solutions have already been described in the patent literature. In this case, inter alia, the following principles of operation are used:                determination of the impedance of the actuator coil by means of a high-frequency bridge circuit, and comparison with a reference inductance or a further actuator coil for the same magnetic bearing axis (DE 42107411),        addition modulation of a sinusoidal alternating current onto the current through the actuator coils, and detection and filtering of the resultant position-dependent voltage (EP 0749538).        
With both principles of operation, disadvantages can be expected when they are combined with clocked power output stages, which are often used for applications of this type, because of their low heat losses and small physical size.